RAZA RABBA, SEFER (Aram. סֵפֶר רָזָא רַבָּא; "The Book of the Great Secret"), a work of *Merkabah mysticism which is no longer extant as a separate entity. That it existed, however, cannot be doubted. Several Near Eastern, Palestinian, and Babylonian authors of the ninth, tenth, and 11th centuries who attest to its existence were discovered by Jacob Mann (Mann, Texts, 2 (1935), 74–83). In the polemical works of the leading Karaite sage of Jerusalem, *Daniel b. Moses al-Qumisi (late ninth century), the work is described as having magical content. Another Karaite author writes about the magical acts described in the book: "for love and hate, miraculous shortcuts, and questions in dreams." Raza Rabba is also mentioned in a responsum of *Hai Gaon (B.M. Lewin (ed.), Oẓar ha-Ge'onim, on Ḥagigah (1931), 21). In Sefer Raza Rabba magical content is intertwined with an exposition on the Merkabah, including speculations on the names of angels and demons known from magical literature on oaths, formulations of amulets by Babylonian Arabs from the fifth to eighth centuries, and gematriot which afterward passed on to the *Ḥasidei Ashkenaz.

Raza Rabba differs in character from Midrashim written in France and in Narbonne and apparently derived from an Eastern or Babylonian source which reached Germany and groups of Ḥasidim. However, it is not clear whether either *Judah he-Ḥasid or *Eleazar of Worms knew the work.

Portions of Raza Rabba were found in a manuscript of a commentary on Sefer *Shi'ur Komah written in the late 13th century by Moses (Azriel) b. Eleazar ha-Darshan ("the preacher"), son of Moses ha-Darshan (the husband of Judah b. Samuel he-Ḥasid's granddaughter in Wuerzburg), and have been published by G. *Scholem . Moses cites a work which he calls Ha-Sod ha-Gadol ("The Great Secret") and quotes other works which leave no doubt that he saw several versions of Raza Rabba or parts of it; he cites Sefer ha-*Bahir as a separate source.

In contrast to extant visionary Merkabah texts, Raza Rabba was a Merkabah Midrash and some elements in it are clearly and unquestionably linked to Sefer ha-Bahir, although they appear in different versions. While Raza Rabba contains no definitely Gnostic homilies, the Sefer ha-Bahir develops the same motifs in a new direction, a kabbalistic-Gnostic one. Sefer ha-Bahir contains the oldest enumeration of the ten Sefirot interpreted kabbalistically; an older, though incomplete, list is found in Raza Rabba, which was one of the literary sources for the editing of the Bahir. The homiletic symbolism of the Sefirot developed in the Bahir does not occur in Raza Rabba. Other matters treated in the Bahir, such as *gilgul , are not present in the extant portions of Raza Rabba.